A distributed antenna system (DAS) is a technology for providing radio coverage in an area which cannot be directly served from the general mobile radio network (for example, tunnels in a metro system, or a building complex), and is particularly advantageous in applications where multiple wireless service providers need to provide coverage since a single DAS can be used with many radio base stations.
A typical digital DAS is shown in FIG. 1 and consists of head-end equipment, herein referred to as digital master units (DMUs) 14, 15, which receive downlink signals from a number of radio base stations (RBSs) 10-13, and convert them for transport on optical fibers 16, 17 via one or more routing units (RUs) 18 to a number of remote nodes 19, 20, herein referred to as digital remote units (DRUs), located in the coverage area which convert the optical signals into radio signals which can be broadcast on antennas driven by the DRUs 19, 20 for transport to/from wireless communication devices (WCDs) 21, 22 such as smart phones and tablets. Each DRU 19, 20 receives uplink signals from its connected antenna(s) and converts them for transmission over the optical fibers 16, 17 back to the DMUs 14, 15 and onward to the RBSs 10-13.
A modern active DAS, as that illustrated in FIG. 1, transports the radio signals in the form of digital samples, usually over fiber optic connections though not always. Digital data transport allows for flexible routing and distribution of radio signals with a much finer degree of control over which signals go to which DRU.
Base station signals are converted into filtered streams of digital data corresponding to the different carrier frequency allocations, and uplink signals are likewise filtered according to the frequency allocations and sent back to the base stations. The base station interface can be analogue (for instance, with radio frequency (RF) downlink and uplink signals) or digital (where the downlink and uplink signals are encoded in digital form).
When the DAS is correctly configured, it appears as a transparent “pipe” through which the signals are transferred in the downlink and uplink directions with an appropriate gain in each direction set by the system installer.
A significant part of the cost of a DAS installation comes from the number of man-hours required to set up and commission the DAS. For a digital DAS, the main tasks are to define the carrier frequency ranges used by the base stations (so that digital filter center frequencies and bandwidths of the DAS are set appropriately) and to set the correct gain parameters so that the required signal level is achieved in each of the coverage areas. In the event of frequency re-farming by the mobile network operator, where the allocation of frequency ranges to particular technologies is changed—for example when replacing a legacy Global System for Mobile Communications (GSM) system with a Long Term Evolution (LTE) system—this manual work needs to be repeated and further; during this time the DAS will likely not provide any radio coverage.
US 2013/071112 discloses a configuration sub-system for telecommunication systems. The configuration sub-system can include a test signal generator, a power measurement device, at least one additional power measurement device, and a controller. The test signal generator can be integrated into components of a telecommunication system. The test signal generator can provide a test signal to a signal path of the telecommunication system. The power measurement device and the additional power measurement device can respectively be integrated into different components of the telecommunication system. The power measurement device and the additional power measurement device can respectively measure the power of the test signal at different measurement points in the signal path. The controller can normalize signals transmitted via the telecommunication system by adjusting a path gain for the signal path based on measurements from the power measurement device and the additional power measurement device.
WO 97/29608 discloses a method and apparatus for integrating a personal communication system with a cable television plant. A set of radio antenna devices (RAD) are connected to the cable plant. The RADs provide frequency conversion and power control of signal received from the cable plant for wireless transmission to the remote units. The RADs also provide power control and frequency conversion of wireless signals received from the remote units for transmission by the RADs onto the cable plant. In addition to the functions of standard base stations and centralized controller, the CATV base station must also compensate for gain variations in the cable plant. The downstream power control is regulated by a RAD reference signal which can be hidden within the CDMA signal for maximum efficiency.